满足指定条件时，如何用Pandas获取DataFrame的最后一行数据？

First, let's recreate the exact DataFrame from your provided table so we can work with a reproducible example:

import pandas as pd

# Build the sample DataFrame
data = {
    '1': [0, 30, 0, 62, 62, 62],
    '2': [0, 30, 0, 0, 30, 92],
    '3': [0, 0, 0, 0, 0, 92],
    '4': [50, 0, 0, 0, 50, 142],
    '1.1': [0, 0, 0, 62, 62, 62],
    '2.1': [0, 30, 0, 0, 30, 92],
    '3.1': [0, 0, 0, 0, 0, 92],
    '4.1': [50, 0, 0, 0, 50, 142]
}
df = pd.DataFrame(data, index=['w1', 'w2', 'd1', 'd2', 'Total', 'Cumulative'])
df.index.name = 'WS'

Now, let's cover common scenarios for retrieving the last row based on different conditions:

Scenario 1: Get the last row of the entire DataFrame #

If you just need the final row regardless of conditions, use iloc[-1]—this accesses the row at the last position in the DataFrame:

last_row = df.iloc[-1]
# Output will be the 'Cumulative' row

Scenario 2: Get the last row that meets a column-specific condition #

Suppose you want the last row where column '1' has a value greater than 0. First filter the DataFrame to keep only matching rows, then grab the last one:

# Filter rows where column '1' > 0
filtered = df[df['1'] > 0]
# Get the last row of the filtered result
last_matching_row = filtered.iloc[-1]

You can also condense this into a single line:

last_matching_row = df[df['1'] > 0].iloc[-1]

Pro tip: Always check if the filtered DataFrame isn't empty before accessing iloc[-1] to avoid an IndexError:

filtered = df[df['1'] > 0]
if not filtered.empty:
    last_matching_row = filtered.iloc[-1]
else:
    print("No rows satisfy the condition.")

Scenario 3: Get the last row with a specific index label #

If you're targeting rows with a particular index name (like 'Cumulative'), use loc. If there are multiple rows with the same label, iloc[-1] will get the last occurrence:

# For a unique index label
cumulative_row = df.loc['Cumulative']

# If multiple rows have the same label, get the last one
last_cumulative_row = df.loc['Cumulative'].iloc[-1]

Scenario 4: Get the last row where any column meets a condition #

For example, if you want the last row that has at least one non-zero value:

# Check if any value in the row is non-zero
filtered = df[df.any(axis=1)]
last_non_zero_row = filtered.iloc[-1]

These methods cover most common use cases. Adjust the condition in the filter step to match your specific requirements!

内容的提问来源于stack exchange，提问作者Dylan